Bootstrap 3.3.1 - as small as it gets (near-perfect GZIP compression)

Choose a version:

The original file has 67155 bytes (65.6k) and is available from the project website.
There you can find the official minified version, too, which brings down the size to 35601 bytes (34.8k, 53%).

After GZIP compression these minified files vary in size:

Microsoft	12274 bytes (12.0k)	CDN
Boot	11326 bytes (11.1k)	CDN
MaxCDN	11326 bytes (11.1k)	CDN
cdnjs	9524 bytes (9.3k)	CDN
gzip -6 (default)	9464 bytes (9.2k)	local copy
gzip -9	9432 bytes (9.2k)	local copy
unpkg	9426 bytes (9.2k)	CDN
Yandex	9412 bytes (9.2k)	CDN
jsdelivr	9412 bytes (9.2k)	CDN
7zip -mx=9 -tgzip	9123 bytes (8.9k)	local copy
libdeflate -12	9117 bytes (8.9k)	local copy
kzip -s0 -rn -b2	9109 bytes (8.9k)	local copy
zultra	9089 bytes (8.9k)	local copy
pigz -11 -n	9065 bytes (8.9k)	local copy
Zopfli	9058 bytes (8.8k)	local copy

perma-link to the smallest file on my server:
http://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.1.min.js (or via HTTPS)

You will automatically get the smallest Bootstrap 3.3.1 file, ETag caching is available and
if your browser doesn't support GZIP decompression then the uncompressed version will be sent.

Currently best Zopfli settings

Save 354 bytes by using my Bootstrap 3.3.1 Zopfli version instead of the best available CDN (3.91% smaller than jsdelivr, 9058 vs. 9412 bytes):

Download

You can use my super-compressed files for whatever purpose you like as long as you respect the library's original license agreement.
There are no restrictions from my side - but please avoid hot-linking if you run a high-traffic website.

These command-line settings yielded the best compression ratio so far (Linux version of zopfli-krzymod):
zopfli --i1000000 --mb8 --mls4 --bsr18 --lazy --ohh

(found February 26, 2016)

Description	Value	Parameter
iterations	1000000	--i1000000
maximum blocks	8	--mb8
maximum length score	4	--mls4
block splitting recursion	18	--bsr18
lazy matching in LZ77	yes	--lazy
optimized Huffman headers	yes	--ohh
initial random W for iterations	1	--rw1
initial random Z for iterations	2	--rz2

Verify file integrity

After decompression, my uncompressed files are identical to the original ones:

MD5:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.3.1/dist/js/bootstrap.min.js --location | md5sum
2616d3564578d8f845813483352802a9 -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.1.min.zopfli.js.gz | md5sum
2616d3564578d8f845813483352802a9 -

SHA1:
curl --silent --compressed https://raw.githubusercontent.com/twbs/bootstrap/v3.3.1/dist/js/bootstrap.min.js --location | sha1sum
5ada7c103fc1deabc925cc1fdbbb6e451c21fc70 -
curl --silent --compressed https://minime.stephan-brumme.com/files/bootstrap/bootstrap-3.3.1.min.zopfli.js.gz | sha1sum
5ada7c103fc1deabc925cc1fdbbb6e451c21fc70 -

All listed CDNs deliver identical contents:

CDN	Size (compressed)	MD5 (uncompressed)	Timestamp
Microsoft	12274 bytes	2616d3564578d8f845813483352802a9	(invalid)
Boot	11326 bytes	2616d3564578d8f845813483352802a9	(invalid)
MaxCDN	11326 bytes	2616d3564578d8f845813483352802a9	(invalid)
cdnjs	9524 bytes	2616d3564578d8f845813483352802a9	(invalid)
unpkg	9426 bytes	2616d3564578d8f845813483352802a9	July 11, 2016 @ 16:21
Yandex	9412 bytes	2616d3564578d8f845813483352802a9	(invalid)
jsdelivr	9412 bytes	2616d3564578d8f845813483352802a9	(invalid)

Note: only the MD5 hashes are shown to keep things simple.

Other Versions

Available Bootstrap versions at minime.stephan-brumme.com:

5.2.3, 5.2.2, 5.2.1, 5.2.0,
5.1.3, 5.1.2, 5.1.1, 5.1.0,
5.0.2, 5.0.1, 5.0.0,
4.6.0,
4.5.3, 4.5.2, 4.5.1, 4.5.0,
4.4.1, 4.4.0,
4.3.1, 4.3.0,
4.2.1, 4.2.0,
4.1.3, 4.1.2, 4.1.1, 4.1.0, 4.0.0,
3.4.1, 3.4.0,
3.3.7, 3.3.6, 3.3.5, 3.3.4, 3.3.2, 3.3.1, 3.3.0,
3.2.0,
3.1.1, 3.1.0,
3.0.3, 3.0.2, 3.0.1, 3.0.0

The project site contains an overview how well these versions were compressed.
Other interesting projects are AngularJS, BackboneJS, D3, Dojo, Ember, jQuery, Knockout, lodash, React, Socket.IO, ThreeJS, UnderscoreJS and Vue.

Changelog

Best Zopfli parameters so far:

Size	Improvement	Parameters	Found
9058 bytes	-1 byte	zopfli --i1000000 --mls4 --bsr18 --lazy --ohh	February 26, 2016 @ 12:38
9059 bytes	-1 byte	zopfli --i100000 --mls4 --bsr18 --lazy --ohh	September 25, 2015 @ 16:31
9060 bytes	-1 byte	zopfli --i10000 --mls4 --bsr18 --lazy --ohh	September 25, 2015 @ 15:01
9061 bytes	-1 byte	zopfli --i10000 --mls512 --bsr12 --lazy --ohh	September 10, 2015 @ 17:37
9062 bytes	-2 bytes	zopfli --i1000 --mls512 --bsr6 --lazy --ohh	September 10, 2015 @ 16:36
9064 bytes	–	zopfli --i100 --mls4096 --bsr16 --lazy --ohh	September 10, 2015 @ 16:27

If there are multiple parameter sets yielding the same compressed size, only the first one found is shown.

Most recent activity on July 20, 2020 @ 12:56.

Heatmaps

This Zopfli heatmap visualizes how compression changes when modifying the --bsr and --mls parameter.
Cell's contents is the best filesize achieved (in bytes, hover with mouse over cells to see number of iterations).

Good parameters are green, bad are red. The best and worst are bold as well.
The brightness of the blue background color indicates how many iterations were processed:
10,000, 100,000 or 1,000,000.

bsr \ mls	2	4	8	16	32	64	128	256	512	1024	2048	4096	8192	16384	32768
bsr \ mls	2	4	8	16	32	64	128	256	512	1024	2048	4096	8192	16384	32768
2	9070	9070	9070	9070	9069	9070	9069	9068	9070	9071	9073	9072	9064	9069	9063
4	9061	9061	9062	9061	9062	9061	9061	9062	9062	9062	9061	9063	9064	9068	9065
6	9064	9064	9062	9063	9062	9064	9061	9062	9061	9061	9063	9061	9061	9064	9063
7	9058	9058	9061	9061	9062	9062	9061	9062	9061	9062	9064	9061	9064	9062	9068
8	9061	9061	9062	9061	9061	9061	9061	9062	9062	9062	9061	9061	9064	9068	9063
9	9060	9060	9062	9062	9062	9061	9061	9064	9062	9061	9061	9063	9063	9062	9063
10	9061	9061	9061	9061	9061	9062	9062	9061	9061	9062	9062	9065	9062	9068	9063
11	9058	9058	9061	9070	9062	9061	9062	9061	9062	9062	9062	9063	9061	9061	9064
12	9063	9063	9062	9061	9063	9061	9061	9062	9061	9061	9062	9061	9065	9063	9062
13	9060	9060	9062	9061	9062	9062	9062	9062	9062	9063	9062	9065	9064	9062	9064
14	9061	9061	9062	9062	9062	9062	9061	9062	9061	9061	9062	9065	9062	9069	9066
15	9061	9061	9061	9061	9062	9061	9061	9061	9062	9062	9064	9062	9061	9062	9065
16	9061	9061	9062	9061	9062	9061	9062	9063	9062	9061	9061	9061	9062	9069	9063
17	9060	9060	9061	9061	9061	9062	9061	9063	9062	9061	9062	9061	9061	9063	9063
18	9058	9058	9063	9061	9062	9062	9061	9061	9061	9061	9061	9065	9064	9062	9063
19	9058	9058	9062	9061	9062	9062	9061	9062	9062	9062	9062	9062	9061	9068	9068
20	9060	9060	9061	9061	9062	9062	9062	9062	9062	9061	9064	9061	9064	9062	9063
21	9060	9060	9061	9061	9062	9062	9062	9061	9062	9062	9061	9062	9064	9062	9062
22	9060	9060	9061	9061	9062	9061	9062	9061	9062	9062	9062	9061	9062	9062	9064
23	9060	9060	9062	9061	9062	9061	9061	9062	9062	9061	9064	9065	9061	9068	9063
25	9060	9060	9062	9061	9062	9062	9061	9062	9062	9061	9062	9062	9061	9068	9063
30	9061	9061	9062	9061	9062	9064	9062	9061	9062	9063	9062	9062	9063	9069	9063
40	9061	9061	9062	9061	9062	9061	9062	9062	9062	9061	9061	9061	9062	9062	9062

Due to the Monte Carlo design of my search algorithm, not all parameters have reached the same number of iterations yet:

Iterations	Min. Bytes	Reduction	Coverage
100	9062 bytes	–	100%
1,000	9061 bytes	-1 byte	100%
10,000	9060 bytes	-1 byte	100%
100,000	9059 bytes	-1 byte	6.96%
1,000,000	9058 bytes	-1 byte	2.32%
10,000,000	–	–	–

KZIP has far less options available for tuning/optimization. I only played around with the number of blocks (parameter -n):

Blocks	Min. Bytes	Compared To Best Zopfli	Compared To Best KZIP
(any)	9120 bytes	+62 bytes (+0.68%)	+11 bytes
1	9121 bytes	+63 bytes (+0.70%)	+12 bytes
2	9109 bytes	+51 bytes (+0.56%)	–
3	9125 bytes	+67 bytes (+0.74%)	+16 bytes
4	9157 bytes	+99 bytes (+1.09%)	+48 bytes
5	9193 bytes	+135 bytes (+1.49%)	+84 bytes
6	9236 bytes	+178 bytes (+1.97%)	+127 bytes
7	9266 bytes	+208 bytes (+2.30%)	+157 bytes
8	9313 bytes	+255 bytes (+2.82%)	+204 bytes

Non-DEFLATE Algorithms

Archivers based on completely different compression algorithms often produce superior results.
Unfortunately, browsers only support gzip compression at the moment.
However, support for Brotli is constantly growing - for example, your browser actually supports it !

Algorithm	Program	Parameters	Size	Compared To Best Zopfli
RAR (proprietary)	RAR	rar a -m5 -md64m -mc63:128t -mt1	7546 bytes	-1512 bytes (-16.69%)
ZPAQ (Wikipedia)	zpaq	zpaq -method 69	8237 bytes	-821 bytes (-9.06%)
Brotli (Wikipedia)	brotli	brotli -q 11	8354 bytes	-704 bytes (-7.77%)
PPMd (Wikipedia)	7zip	7za a -mx=9 -m0=ppmd	8601 bytes	-457 bytes (-5.05%)
Burrows-Wheeler transform (Wikipedia)	bzip2	bzip2 -9	8802 bytes	-256 bytes (-2.83%)
LZMA2 (Wikipedia)	xz	xz -9	9020 bytes	-38 bytes (-0.42%)
Zstandard (Wikipedia)	zstd	zstd -19	9075 bytes	+17 bytes (+0.19%)

Detailled Analysis

I wrote a DEFLATE decoder in Javascript. Click the button below to start a client-side analysis of the smallest gzipped files (may take a second):

Load and Parse Data

Notes: pigz is a fast open source multi-threaded implementation of gzip written by one of the original authors of gzip.
However, when using compression level 11, pigz actually switches to the slower Zopfli algorithm and isn't multi-threaded anymore.
KrzyMOD's extensions to Zopfli offer the highest level of configuration and is therefore used for my brute-force search.
Ken Silverman wrote the closed-source KZIP compression program and Jonathon Fowler ported it to Linux.
Defluff was created by Joachim Henke; DeflOpt is a tool by Ben Jos Walbeehm.

website made by Stephan Brumme in 2015 and still improving in 2026.
all timestamps are displayed in central european time. see my changelog.
no flash, not even images or external css files - and everything squeezed into a single html file.
which was handsomely compressed before releasing it into the wild internet - obviously.

please visit my homepage and my blog, too.
email: minime (at) stephan-brumme.com

All trademarks are property of their respective owners. You know, the boring legal stuff.